Network system time domain re-stamping

ABSTRACT

One embodiment of the invention includes a coax media converter (CMC) system communicatively coupled to at least one modem in a network system. The system includes a frequency reference configured to generate a clock signal in a local time domain. The system also includes a scheduling processor configured to extract a bandwidth allocation message from a data stream and to re-stamp each of at least one timestamp in the bandwidth allocation message in the local time domain based on the clock signal to generate a corresponding updated bandwidth allocation message comprising a respective at least one re-stamped timestamp. The system further includes a downstream physical interface configured to transmit the updated bandwidth allocation message to the at least one modem to schedule upstream burst transmissions from the respective at least modem based on the at least one re-stamped timestamp.

TECHNICAL FIELD

This disclosure relates to network system time domain re-stamping.

BACKGROUND

Some network systems implement a variety of media through which data istransmitted. For example, a Hybrid Fiber Coaxial (HFC) cable accessnetwork can be implemented in a network system to provide broadcastmedia (e.g., a motion picture experts group (MPEG) data stream) for aplurality of subscribers over an optical fiber medium that is convertedto a coaxial cable medium. In such a network system, cable modems canprovide requests for bandwidth and implement data communications, suchas according to a Data-Over-Cable Service Interface Specification(DOCSIS). For example, the cable modem can communicate with upstreamnetwork equipment in the network system via upstream burst transmissionsthat can be allocated by a bandwidth allocation message (e.g., anUpstream Bandwidth Allocation Map (MAP) message) that is provided from anetwork termination system (e.g., a cable modem termination system(CMTS)). Accordingly, the cable modems can schedule respective upstreamburst transmissions according to the timing set forth in the bandwidthallocation message.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a network system.

FIG. 2 illustrates an example of a bandwidth allocation message.

FIG. 3 illustrates an example of a Coax Media Converter (CMC).

FIG. 4 illustrates an example of a timing diagram.

FIG. 5 illustrates an example of a method for scheduling upstream bursttransmissions from at least one modem.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

This disclosure relates generally to network systems, and specificallyto network system time domain re-stamping. In a network system, a CoaxMedia Converter (CMC) can interconnect a network termination system(e.g., a modular cable modem termination system (M-CMTS)) and aplurality of cable modems (e.g., each corresponding to a givensubscriber). The network termination system can be configured togenerate bandwidth allocation messages that each provides timeslots todesignate respective times in which the cable modems can scheduleupstream burst messages, with each of the timeslots being dictated byrespective timestamps. The CMC can be remotely located relative to thenetwork termination system and connected with the network system (e.g.,via an optical fiber connection). The CMC thus can implement a separatetime domain from the network termination system, such as based on havingdifferent clocks. The CMC can extract the bandwidth allocation messages,such as from a data stream (e.g., a motion picture experts group (MPEG)data stream), analyze the timestamps in the bandwidth allocationmessage, and modify (e.g., re-stamp) the timestamps in a local timedomain.

The updated bandwidth allocation message can then be inserted into thedata stream to be transmitted to the cable modems. The cable modems canthus schedule respective upstream burst transmissions based on there-stamped timestamps in the local domain provided by the CMC. The CMCcan receive the upstream burst transmissions that are provided at thetimes designated in the updated bandwidth allocation message and canpacketize the upstream burst transmissions for transmission upstream tothe network termination system. The algorithm implemented by the CMC forthe re-stamping of the timestamps in the bandwidth allocation messagecan be programmed to accommodate an underscheduling condition, such asresulting from the clock in the time domain of the network terminationsystem being slower than the clock in the time domain of the CMC.Additionally, the CMC can be configured to detect an overschedulingcondition, such as resulting from the clock in the time domain of thenetwork termination system being faster than the clock in the timedomain of the CMC. In response, as one example, the CMC can instruct thenetwork termination system to adjust the speed of the clock in thenetwork termination system time domain. As another example, the CMC canimplement re-stamping of the timestamps in the bandwidth allocationmessage in a manner that mitigates contention region timing, and thuscan accommodate the scheduling of upstream burst transmissions in lesstime.

Example Embodiments

FIG. 1 illustrates an example of a network system 10. The network system10 can be configured as any of a variety of networks, such as a HybridFiber Coaxial (HFC) cable access network that can be implemented in anetwork system to provide broadcast media for a plurality ofsubscribers. The network system 10 includes a network termination system(TS) 12 that can provide connectivity to a wide area network, such asincluding the Internet, demonstrated at 14.

As an example, the network TS 12 can be a modular cable modemtermination system (M-CMTS) that is configured for operation accordingto one of Data-Over-Cable Service Interface Specification (DOCSIS)network standards. The network TS 12 can thus operate as a service flowengine to a plurality of network service subscribers in the networksystem 10. The network TS 12 can also be coupled to a variety ofadditional network components and resources (not shown), such as apolicy server, a provisioning system, and/or other service providercomponents.

The network system 10 also includes a Coax Media Converter (CMC) 16 thatcan be coupled to the network TS 12, such as via a fiber-opticconnection. The CMC 16 can be an apparatus that interconnects thenetwork TS 12 and a plurality N of cable modems 18, where N is apositive integer denoting the number of cable modems. As an example, thecable modems 18 can be coupled to the CMC 16 via respective coaxialcable connections. In such example, the CMC 16 can be configured toprovide an interface between the optical connection to the network TS 12and the coaxial connection to the cable modems 18. For example, the CMC16 can be configured (e.g., according to a DOCSIS standard) to convertan optical data stream from the network TS to a corresponding electricaldata stream and to convert electrical data streams from cable modems tooptical data streams for transmission to the network TS.

The network TS 12 can include a scheduling entity 20 and a first timedomain 22 that can be defined by a clock system in the network TS 12.The scheduling entity 20 is configured to generate a bandwidthallocation message, such as an Upstream Bandwidth Allocation Map (MAP)message, that can include instructions to allocate bandwidth to thecable modems 18, such as in a time-division multiplexed manner. Forexample, each of the cable modems 18 can correspond to a givensubscriber that can have a respective subscriber plan, such defining anamount of bandwidth (e.g., upstream and/or downstream) available to therespective cable modem 18. The bandwidth allocation message that isgenerated by the scheduling entity 20 can specify time slots for therespective cable modems 18 in which the cable modems 18 can provideupstream burst data transmissions for requesting bandwidth and/orrequesting digital media. The time slots in the bandwidth allocationmessage can be defined by the scheduling entity 20 according torespective timestamps in the respective time domain. The time slots arescheduled at future times that can instruct the respective cable modems18 when to provide the respective upstream burst transmissions. The CMC16 can, upon receiving the upstream burst transmissions, packetize theupstream burst transmissions to provide a corresponding data packet tothe network TS 12.

FIG. 2 illustrates an example of a bandwidth allocation message 50. Forexample, the bandwidth allocation message 50 can correspond to a MAPmessage in a DOCSIS network system. The bandwidth allocation message 50can be generated, for example, by the scheduling entity 20 in thenetwork TS 12 in the example of FIG. 1. Therefore, reference is to bemade to the example of FIG. 1 in the following description of theexample of FIG. 2.

The bandwidth allocation message 50 includes a plurality X of bursttransmission time slots 52, where X is a positive integer denoting thenumber of time slots. Each time slot thus can correspond to an intervalof time within which a given one of the cable modems 18 is to begintransmission of a respective upstream burst transmission. Each of theburst transmission time slots 52 can be defined by a respective one ormore timestamps 54. For example, a given time stamp can specify abeginning time of the respective burst transmission time slot 52 or itcan specify a beginning and end time of the respective bursttransmission time slot 52. The timestamps 54 can thus correspond tofuture times at which the respective cable modems 18 can begin and/orend their respective upstream burst transmission to the CMC 16. Each ofthe burst transmission time slots 52 can correspond to a given one ofthe cable modems 18, such that a given one of the cable modems 18 can beassociated with one or more of the burst transmission time slots 52 inthe bandwidth allocation message 50.

The bandwidth allocation message 50 also includes a plurality X−1 ofcontention regions 56 that are interleaved with the burst transmissiontime slots 52. The contention regions 56 can correspond to spaces intime between the burst transmission time slots 52, such as to providetemporal gaps between consecutive transmissions of respective upstreamburst transmissions from respective separate cable modems 18. Thecontention regions 56 can be defined based on contention regiontimestamps 58. While the bandwidth allocation message 50 is demonstratedas including both the timestamps 54 corresponding to the bursttransmission time slots 52 and the timestamps 58 corresponding to thecontention regions 56, it is to be understood that the contention regiontimestamps 58 could correspond to the timestamps 54 of the bursttransmission time slots 52. For example, a given contention region 56can be defined by an end timestamp 54 of a preceding burst transmissiontime slot 52 and by a beginning timestamp 54 of a subsequent bursttransmission time slot 52, such that the given contention region 56 doesnot require a dedicated timestamp 58 but instead can be defined based onone or more existing burst transmission time slots allocated for otherpurposes.

Additionally, the bandwidth allocation message 50 can include anacknowledgement 60 that includes an acknowledgement timestamp 62. Theacknowledgement 60 can indicate via the acknowledgement timestamp 62 apast time corresponding to an end time when the network TS 12 receivedthe last and most recent upstream burst transmission provided from thecable modems 18. Thus, the cable modems 18 can utilize theacknowledgement timestamp 62 to determine if previously providedupstream burst transmissions were received by the network TS 12. Forexample, in response to determining that a given upstream bursttransmission was not received by the network TS 12, such as based on theacknowledgement timestamp 62 preceding the time of transmission of thegiven upstream burst transmission, the cable modem 18 can attempt tore-transmit the given upstream burst transmission.

Referring back to the example of FIG. 1, the scheduling entity 20 in thenetwork TS 12 can define the timestamps 54, 58, and 62 of the bandwidthallocation message 50 in the first time domain 22, such as based on aclock system that is local to the network TS 12 (e.g., a 10.24 MHzclock). In some examples, however, based on geographic separation ofvarious parts of the system 10, the CMC 16 may not be able to operate inthe first time domain 22. Therefore, the CMC 16 includes a second timedomain 24 that can be based on a clock system that is local to the CMC16, which is different from the first time domain 22. As an example, thefrequency of the clock signal in the second time domain 24 can have afrequency that is approximately equal to the clock signal in the firsttime domain 22 (e.g., 10.24 MHz). However, physical (e.g., spatial)separation and lack of common clock source can cause differences betweenthe first and second time domains 22 and 24. For example, thedifferences can be due to phase differences, drift, and asymmetricalsignal transmission between the network TS 12 and the CMC 16. Thus,because the timestamps 54, 58, and 62 are provided in the first timedomain 22, the CMC 16 may not be able to properly receive the upstreamburst transmissions based on timing mismatches between the first andsecond time domains 22 and 24. Therefore, the CMC 16 includes ascheduling processor 26 that is configured to implement re-stamping ofthe timestamps 54, 58, and 62 of the bandwidth allocation message 50 inthe second time domain 24.

As an example, the scheduling processor 26 can be configured to executeinstructions for implementing a re-stamping algorithm that is configuredto analyze the bandwidth allocation message 50 to determine relativetiming between the respective timestamps 54, 58, and 62, and to re-stampthe respective timestamps 54, 58, and 62 in the second time domain 24.The re-stamped timestamps can be provided in an updated bandwidthallocation message that is transmitted by the CMC 16 to the cable modems18. Therefore, the cable modems 18 can be provided with timestamps thatare provided in the second time domain 24, such that the timing of theupstream burst transmissions from the cable modems 18 to the CMC 16 canbe substantially consistent to substantially mitigate timing mismatchesbetween the network TS 12 and the CMC 16. In other words, the schedulingprocessor 26 can operate in the second time domain 24 and cansubstantially maintain consistent upstream bandwidth allocations of thecable modems 18 as set forth in the bandwidth allocation message 50generated by the scheduling entity 20 in the first time domain 22.

FIG. 3 illustrates an example of a CMC 100. The CMC 100 can correspondto the CMC 16 the example of FIG. 1, such that the CMC 100 caninterconnect the network TS 12 via a fiber-optic communication link anda plurality of the cable modems 18 via coaxial cable connections.Therefore, reference can be made to the example of FIGS. 1 and 2 in thefollowing description of the example of FIG. 3 for additional context.

The CMC 100 includes a scheduling processor 102 that includes a messagesniffer 104 and a re-stamp component 106. The message sniffer 104 can beconfigured to monitor a data stream DS that can be provided from thenetwork TS 12 for a bandwidth allocation message provided by the networkTS 12. As an example, the data stream DS can be a Motion Picture ExpertsGroup (MPEG) data stream carried within an Internet Protocol (IP) datatunnel (e.g., a Downstream External PHY Interface (DEPI) tunnel). Thedownstream data stream DS can contain IP data packets (e.g., comprisingone or more MPEG frames), and the message sniffer 104 can be configuredto monitor the IP packets within the MPEG data stream. The messagesniffer 104 thus can monitor the IP data tunnel for detecting a MAPmessage. In response to detecting the MAP message, the message sniffer104 can extract the bandwidth allocation message MP from the IP datatunnel and can provide the bandwidth allocation message MP to there-stamp component 106.

The re-stamp component 106 can implement an algorithm that is configuredto analyze the timestamps 54, 58, and 62 that are provided in the firsttime domain 22 to determine relative timing between the timestamps 54,58, and 62. The re-stamp component 106 can thus implement re-stamping ofthe timestamps 54, 58, and 62 in the second time domain 24 based on therelative timing determined for the respective timestamps. In the exampleof FIG. 3, the CMC 100 includes a second time domain (TD2) frequencyreference 108, which can be configured as a phase-locked loop thatgenerates a clock signal CLK having a frequency that is approximatelythe same as the clock system in the first time domain 22 (e.g., 10.24MHz). Thus, the re-stamp component 106 can be configured to generateupdated timestamps in the second time domain 24 based on the clocksignal CLK, such as based on the relative timing of the timestamps 54,58, and 62 in the first time domain 22 and based on sufficient latencyof transmission of an updated bandwidth allocation message to the cablemodems 18.

As an example, the re-stamping algorithm that can be implemented by there-stamp component 106 in a DOCSIS network system can be demonstrated bythe following pseudo-code:

ALGORITHM 1 void map_re_stamping (ds-channel, map_pkt) {   //   // init& setup...   // look up the ID space and associated working contextblock   //   map_generation =   map_pkt->startAlloc <<UsLch->mslot1024_scale;   if (map_generation !=UsPhy->GenerationTimestamp_1024)   {     //     // new generation of mapfrom the Us Scheduler Entity.     //     UsPhy->GenerationTimestamp_1024= map_generation;     UsLch->primaryDsMapReplCount = 0;     // check ifthe last mapEndTime is still within the min-map-adv     time.     If(UsPhy->mapEndTimestamp_1024 <       (current_timestamp +UsPhy->MinMapAdvanced))     {       // need to reset startAllocTimestamp      UsPhy->startAllocTimestamp_1024 =       current_timestamp +        UsPhy->NomMapAdvanced;     }     //     // update all logicalchannels' startAllocationTimestamp     //     FOR_ALL_LOGICAL_CHANNEL( )    {       UsLch->startAllocTimestamp_mslot =        UsPhy->startAllocTimestamp_1024 >>        UsLch->mslot1024Scale;     }   }   // now, it is ok to re-stampthe start allocation time.   map_pkt->startAlloc =UsLch->startAllocTimestamp_mslot;   // compute and save theUsLch->mapEndTimestamp_mslot.   // compare it to theUsPhy->mapEndTimestamp_1024, and save the   farthest into future.   //also saves it as the next mapStartAllocTimestamp_1024.   // check if themapEndTimestamp is exceeding the (current-time +   mapEndThreshold)   //to see if this is too far into future, which indicates over-run / over-  scheduling scenario. }

Upon generating the updated timestamps in the second time domain 24 thatis dictated by the TD2 frequency reference 108, the re-stamp component106 is configured to generate an updated bandwidth allocation messageMP_RS, which can be stored in memory. The updated bandwidth allocationmessage MP_RS includes the updated timestamps in the second time domain24. The generation of the updated bandwidth allocation message MP_RS canbe performed in a variety of ways, such as based on replacing theprevious bandwidth allocation message MP with the updated bandwidthallocation message MP_RS, or by replacing the timestamps 54, 58, and 62in the previous bandwidth allocation message MP to provide the previousbandwidth allocation message MP. Thus, as described herein, the terms“re-stamp” and “re-stamping” of the timestamps of the bandwidthallocation message MP can encompass replacing the timestamps generatedby the scheduling entity 20 in the first time domain 22 withcorresponding timestamps in the second time domain 24, either in a new(i.e., updated) corresponding bandwidth allocation message or insertedinto the pre-existing bandwidth allocation message.

The updated bandwidth allocation message MP_RS is provided from there-stamp component 106 to an upstream physical (PHY) interface 110. Theupstream PHY interface 110 can thus save the updated bandwidthallocation message MP_RS in the memory, such that the upstream bursttransmissions from the cable modems 18 can be collected by the upstreamPHY interface 110 for packetization. The updated bandwidth allocationmessage MP_RS is also provided to a downstream PHY interface 114. Thedownstream PHY interface 114 can thus transmit the data stream and theupdated bandwidth allocation message MP_RS, demonstrated collectively asa signal DS_RS, to the cable modems 18. As an example, the updatedbandwidth allocation message MP_RS and the data stream can betransmitted separately to the cable modems 18. As another example, theupdated bandwidth allocation message MP_RS can be inserted into the datastream DS, such as via a stream update component (not shown).

In response to receiving the data stream DS_RS that includes the updatedbandwidth allocation message MP_RS, the cable modems 18 can transmitrespective upstream burst transmissions at future times that aredictated by the re-stamped timestamps in the updated bandwidthallocation message MP_RS. The upstream PHY interface 110 can thusreceive the upstream burst transmissions at the appropriate timescorresponding to the respective cable modems 18 (e.g., at adjustedupstream burst time slots based on the re-stamped timestamps). Theupstream PHY interface 110 can thus generate a data packet that includesthe upstream burst transmissions. The upstream PHY interface 110 canthus transmit the data packet to the network TS via the fiber-opticconnection, demonstrated via the signal US_PCKT.

As a result of the re-stamping of the timestamps in the bandwidthallocation signal MP in the first time domain 22 with updated timestampsin the second time domain 24, the CMC 100 and the network TS 12 cancooperate in separate time domains to communicate with substantiallyreduced timing problems. However, because the clock system in the firsttime domain 22 can be a separate physical clock relative to the TD2frequency reference 108 in the second time domain 24, clock drift canstill occur, even at the same approximate frequency of the respectiveclocks. Therefore, underscheduling and overscheduling conditions mayoccur with the scheduling of the upstream burst transmissions based onthe re-stamping of the timestamps of the bandwidth allocation message MPto generate the updated bandwidth allocation message MP_RS.

In an underscheduling condition, the clock system in the first timedomain 22 can be slower than the TD2 frequency reference 108 in thesecond time domain 24. Such a slower frequency reference in the firsttime domain 22 relative to the second time domain 24 can result in adelay between the transmission of packets generated by the upstream PHYinterface 110 as the CMC 100 consumes bandwidth allocation messages MPfaster than the scheduling entity 20 can create bandwidth allocationmessages. In other words, in an underscheduling condition, the endtimestamps of the bandwidth allocation messages will fall behind.However, based on the analysis of the timestamps 54, 58, and 62 in thebandwidth allocation message MP by the re-stamp component 106, the startallocation time of a given updated bandwidth allocation message MP_RSwill be reset and hence moved forward in time, creating a slight gap intransmission of upstream burst transmissions and/or the packet US_PCKT.The frequency of the occurrence of an underscheduling condition dependson how much slower the clock system of the first time domain 22 isrelative to the TD2 frequency reference 108 in the second time domain24. As a result, underscheduling conditions that may occur between thefirst and second time domains 22 and 24 do not prohibit the re-stampingof the timestamps in the bandwidth allocation message MP, and aresimilar a control plane software disabling interrupt that delaysupstream scheduling, such as can occur in existing CMTS systems.

In an overscheduling condition, the clock system in the first timedomain 22 can be faster than the TD2 frequency reference 108 in thesecond time domain 24. Such a faster frequency reference in the firsttime domain 22 relative to the second time domain 24 can result in ademand for upstream burst transmissions that will cause the upstream PHYinterface 110 to fall behind in providing the packet US_PCKT as the CMC100 consumes bandwidth allocation messages MP slower than the schedulingentity 20 can create bandwidth allocation messages. The CMC 100 candetect an overscheduling condition, such as via the scheduling processor102, based on a last upstream burst timeslot 52 having an associatedtimestamp 54 that is further in time than a predetermined thresholdtime. The threshold can be set to a time interval that is apredetermined time from a timestamp 54 associated with a first upstreamburst timeslot 52. In response to detecting an overscheduling condition,the CMC 100 can substantially mitigate the overscheduling condition.

As an example, in response to the scheduling processor 102 detecting theoverscheduling condition, the CMC 100 can provide a signal to thenetwork TS 12 to adjust the timing of the first time domain 22. The CMC100 (e.g., via the scheduling processor 102) can command the upstreamPHY interface 110 to generate a signal CLK_ADJ having a frequency thatis separate from a frequency of the data stream DS and/or a frequency ofthe packets US_PCKT. The signal CLK_ADJ can thus be indicative of theoverscheduling condition, and can be interpreted by the network TS 12 tosubstantially adjust the timing in the first time domain 22. As anexample, the signal CLK_ADJ can reduce a frequency of the clock systemin the first time domain 22. As another example, the signal CLK_ADJ canadjust the timing of the scheduling entity 20 with respect to thegeneration of the timestamps in the bandwidth allocation message MP,such as to slightly increase a time duration between consecutivetimestamps 54 and/or 58, and/or to decrease a frequency at which thebandwidth allocation messages MP are transmitted to the CMC 100.

As another example, in response to detecting the overschedulingcondition, the re-stamp component 106 can be configured to re-stamp thebandwidth allocation message MP to accommodate the overschedulingcondition. For example, the re-stamp component 106 can substantiallyreduce the duration of contention regions 56 between the respectiveconsecutive burst transmission timeslots 54, such as to provide for thesufficient number of upstream burst transmissions in a lesser durationof time. As another example, the re-stamp component 106 cansubstantially eliminate the contention regions 56 between the respectiveconsecutive burst transmission timeslots 54.

FIG. 4 illustrates an example of a timing diagram 150. The timingdiagram 150 includes the timing of a bandwidth allocation message,demonstrated at 152, and the timing of an updated bandwidth allocationmessage, demonstrated at 154. In the example of FIG. 4, the timing ofthe bandwidth allocation message 152 and the updated bandwidthallocation message 154 are substantially time-aligned with respect to abeginning of the respective bandwidth allocation messages 152 and 154,which thus may not be the same in real time.

The bandwidth allocation message 152 includes a plurality of bursttransmission timeslots 156 that are each separated by a plurality ofcontention regions 158. In the example of FIG. 4, a first timeslot 156has a timestamp T₀ indicating a future time for an upstream bursttransmission from a cable modem 18, and a first contention region 158has a timestamp T₁ indicating an end of the first timeslot 156. A secondtimeslot 156 has a timestamp T₂ that indicates a future time after thetimestamp T₁ for an upstream burst transmission from a cable modem 18,and thus defines the end of the first contention region 158, which has aduration between the time T₁ and the time T₂. Similarly, a secondcontention region 158 begins at a time indicated by a timestamp T₃, athird timeslot 156 begins at a later time indicated by a timestamp T₄, athird contention region 158 begins at a time indicated by a timestampT₅, a fourth timeslot 156 begins at a later time indicated by atimestamp T₆, and a fourth contention region 158 begins at a timeindicated by a timestamp T₇, ending at a time indicated by a timestampT₈. Therefore, the timestamps T₀ through T₈ are timestamps in the firsttime domain 22.

As described previously, in response to the detection of theoverscheduling condition, the re-stamp component 106 can be configuredto re-stamp the timestamps of the bandwidth allocation message MP tosubstantially eliminate the contention regions 158. In the example ofFIG. 4, the re-stamp component 106 can re-stamp the first timestamp T₀in the first time domain 22 as a timestamp T₉ in the second time domain24 corresponding to the beginning of the first timeslot 158. Similarly,the re-stamp component 106 can re-stamp the second timestamp T₁ as atimestamp T₁₀ corresponding to the end of the first timeslot 158, andthus preserving the time duration of the first timeslot 158. However,the re-stamp component 106 can re-stamp the timestamp T₂, correspondingto the beginning of the second timeslot 156 as the timestamp T₁₀, thusomitting the first contention region 158 between the first and secondtimeslots 156. Similarly, the re-stamp component can re-stamp thetimestamps T₃ and T₄ as a timestamp T₁₁ corresponding to the beginningof the third timeslot 158, can re-stamp the timestamps T₅ and T₆ as atimestamp T₁₂ corresponding to the beginning of the fourth timeslot 158,and can re-stamp the timestamps T₇ and T₈ as a timestamp T₁₃corresponding to the beginning of a fifth timeslot 158. The re-stampcomponent 106 can also provide a timestamp T₁₄ corresponding to an endof the fifth timeslot 158. Therefore, the timestamps T₉ through T₁₄ aretimestamps in the second time domain 24.

As demonstrated in the timing diagram 150, in substantially the sameduration of time, the updated bandwidth allocation message 154 includesan additional timeslot 156 relative to the bandwidth allocation message152 based on the substantial elimination of the contention regions 158between the timeslots 156 in the bandwidth allocation message 156.Therefore, the re-stamp component 106 can substantially mitigate theoverscheduling condition based on providing for the scheduling of thesufficient (e.g., required) number of upstream burst transmissions in alesser duration of real time. It is to be understood that, in theexample of FIG. 4, the contention regions 158 are demonstrated to beeliminated in the updated bandwidth allocation message 154 forsimplicity of demonstration, and that the re-stamp component 106 couldinstead be configured to substantially reduce the contention regions 158to mitigate the overscheduling condition.

In view of the foregoing structural and functional features describedabove, a method in accordance with various aspects of the presentinvention will be better appreciated with reference to FIG. 5. While,for purposes of simplicity of explanation, the methods of FIG. 5 isshown and described as executing serially, it is to be understood andappreciated that the present invention is not limited by the illustratedorder, as some aspects could, in accordance with the present invention,occur in different orders and/or concurrently with other aspects fromthat shown and described herein. Moreover, not all illustrated featuresmay be required to implement a method in accordance with an aspect ofthe present invention. The methods or portions thereof can beimplemented as instructions stored in a non-transitory storage medium aswell as be executed by a processor of a computer device, for example.

FIG. 5 illustrates an example of a method 200 for scheduling upstreamburst transmissions from at least one modem (e.g., the cable modems 18).At 202, a bandwidth allocation message (e.g., the bandwidth allocationmessage 50) is extracted from a data stream (e.g., an MPEG data stream)carried within an IP data tunnel (e.g., in the data stream DS) providedfrom a network termination system (e.g., the network TS 12). At 204,each of at least one timestamp (e.g., the timestamps 54, 58, and/or 62)in the bandwidth allocation message is re-stamped based on a clocksignal (e.g., the clock signal CLK provided by the TD2 frequencyreference 108) in a local time domain (e.g., the second time domain 24).At 206, a corresponding updated bandwidth allocation message (e.g., theupdated bandwidth allocation message MP_RS) is generated. The updatedbandwidth allocation message can include one or more respectivere-stamped timestamp that has been generated. At 208, the updatedbandwidth allocation message is provided to at least one modem via adownstream physical interface (e.g., the downstream PHY interface 114)to schedule the upstream burst transmissions from the respective atleast modem based on the at least one re-stamped timestamp.

What have been described above are examples. It is, of course, notpossible to describe every conceivable combination of components ormethods, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations are possible. Accordingly, theinvention is intended to embrace all such alterations, modifications,and variations that fall within the scope of this application, includingthe appended claims.

Where the disclosure or claims recite “a,” “an,” “a first,” or “another”element, or the equivalent thereof, it should be interpreted to includeone or more than one such element, neither requiring nor excluding twoor more such elements. As used herein, the term “includes” meansincludes but not limited to, the term “including” means including butnot limited to. The term “based on” means based at least in part on.

What is claimed is:
 1. An apparatus comprising: a frequency referenceconfigured to generate a clock signal in a local time domain; ascheduling processor configured to: extract a bandwidth allocationmessage from a data stream and to re-stamp each of at least onetimestamp in the bandwidth allocation message in the local time domainbased on the clock signal, generate a corresponding updated bandwidthallocation message comprising a respective at least one re-stampedtimestamp, and monitor the data stream provided in a data tunnel from anetwork termination system for the bandwidth allocation message and toextract the bandwidth allocation message for processing via thescheduling processor; and a physical interface configured to transmitthe updated bandwidth allocation message to schedule upstream bursttransmissions of data from at least one modem based on the at least onere-stamped timestamp.
 2. The apparatus of claim 1, wherein thescheduling processor comprises a re-stamp component configured toanalyze upstream bandwidth allocations corresponding to the at least onetimestamp in the bandwidth allocation message and to assign the at leastone re-stamped timestamp in the local time domain to substantiallymaintain the upstream bandwidth allocations.
 3. The apparatus of claim1, wherein the updated bandwidth allocation message is provided fordownstream transmission by the physical interface within the data tunnelto the at least one modem.
 4. The apparatus of claim 1, wherein thephysical interface is a downstream physical interface, the systemfurther comprising an upstream physical interface configured to receivethe updated bandwidth allocation message from the scheduling processor,to receive the upstream burst transmissions from the at least one modembased on the at least one re-stamped timestamp, and to packetize theupstream burst transmissions for transmission to a network terminationsystem in the network system.
 5. The apparatus of claim 1, wherein thescheduling processor is configured to determine an overschedulingcondition based on at least one of the at least one re-stamped timestampexceeding a predetermined threshold time, the overscheduling conditioncorresponding to a clock signal in a remote time domain of a networktermination system being faster than the clock signal in the local timedomain.
 6. The apparatus of claim 5, wherein the scheduling processor isconfigured, in response to determining the overscheduling condition, totransmit a timing message to the network termination system in afrequency band separate from a frequency band associated with the datastream to instruct the network termination system to decrease afrequency of the clock signal in the remote time domain.
 7. Theapparatus of claim 5, wherein the bandwidth allocation message comprisesat least one contention region of time between each upstreamtransmission time slot associated with the at least one timestamp, andwherein the scheduling processor is configured, in response todetermining the overscheduling condition, to re-stamp each of the atleast one timestamp in the bandwidth allocation message in the localtime domain to reduce the at least one contention region of time.
 8. Theapparatus of claim 1, wherein the scheduling processor is furtherconfigured to re-stamp an acknowledgement in the bandwidth allocationmessage in the local time domain based on the clock signal to generate are-stamped acknowledgement and to insert the re-stamped acknowledgementinto the updated bandwidth allocation message, the re-stampedacknowledgement corresponding to a time that a network terminationsystem received the upstream burst transmissions.
 9. A methodcomprising: extracting a bandwidth allocation message from a data streamof an Internet Protocol (IP) data tunnel provided from a networktermination system; re-stamping each of at least one timestamp in thebandwidth allocation message based on a clock signal in a local timedomain that is separate from a time domain of the network terminationsystem; generating a corresponding updated bandwidth allocation messagecomprising a respective at least one re-stamped timestamp; providing theupdated bandwidth allocation message to at least one modem via adownstream physical interface to schedule the upstream bursttransmissions from the at least modem based on the at least onere-stamped timestamp; comparing each of the at least one re-stampedtimestamp with a predetermined threshold time; and determining anoverscheduling condition based on at least one of the at least onere-stamped timestamp exceeding the predetermined threshold time, theoverscheduling condition corresponding to a clock signal in a remotetime domain associated with an upstream termination system being fasterthan the clock signal in the local time domain.
 10. The method of claim9, further comprising transmitting a timing message to the networktermination system in a frequency band separate from a frequency bandassociated with the IP data tunnel to instruct the termination system todecrease a frequency of the clock signal in the remote time domain inresponse to determining the overscheduling condition.
 11. The method ofclaim 9, wherein the bandwidth allocation message comprises at least onecontention region of time between each upstream transmission time slotassociated with the at least one timestamp, wherein re-stamping each ofat least one timestamp comprises re-stamping each of the at least onetimestamp in the bandwidth allocation message in the local time domainto reduce the at least one contention region of time in response todetermining the overscheduling condition.
 12. The method of claim 9,further comprising: providing the updated bandwidth allocation messageto an upstream physical interface; receiving the upstream bursttransmissions from the at least one modem based on the at least onere-stamped timestamp; and packetizing the upstream burst transmissionsfor transmission to the network termination system.
 13. The method ofclaim 9, wherein the method further comprises: re-stamping anacknowledgement in the bandwidth allocation message in the local timedomain based on the clock signal to generate a re-stampedacknowledgement, the acknowledgement corresponding to a time that thenetwork termination system received the upstream burst transmissions;and inserting the re-stamped acknowledgement into the updated bandwidthallocation message.
 14. An apparatus comprising: a frequency referenceconfigured to generate a clock signal in a local time domain; ascheduling processor configured to: extract a bandwidth allocationmessage from a data stream and to re-stamp each of at least onetimestamp in the bandwidth allocation message in the local time domainbased on the clock signal, generate a corresponding updated bandwidthallocation message comprising a respective at least one re-stampedtimestamp; determine an overscheduling condition based on at least oneof the at least one re-stamped timestamp exceeding a predeterminedthreshold time, the overscheduling condition corresponding to a clocksignal in a remote time domain of a network termination system beingfaster than the clock signal in the local time domain; and a physicalinterface configured to transmit the updated bandwidth allocationmessage to schedule upstream burst transmissions of data from at leastone modem based on the at least one re-stamped timestamp.
 15. Theapparatus of claim 14, wherein the scheduling processor comprises are-stamp component configured to analyze upstream bandwidth allocationscorresponding to the at least one timestamp in the bandwidth allocationmessage and to assign the at least one re-stamped timestamp in the localtime domain to substantially maintain the upstream bandwidthallocations.
 16. The apparatus of claim 14, wherein the schedulingprocessor is further configured to monitor the data stream provided in adata tunnel from a network termination system for the bandwidthallocation message and to extract the bandwidth allocation message forprocessing via the scheduling processor.
 17. The apparatus of claim 16,wherein the updated bandwidth allocation message is provided fordownstream transmission by the physical interface within the data tunnelto the at least one modem.
 18. The apparatus of claim 14, wherein thephysical interface is a downstream physical interface, the systemfurther comprising an upstream physical interface configured to receivethe updated bandwidth allocation message from the scheduling processor,to receive the upstream burst transmissions from the at least one modembased on the at least one re-stamped timestamp, and to packetize theupstream burst transmissions for transmission to a network terminationsystem in the network system.
 19. The apparatus of claim 14, wherein thescheduling processor is configured, in response to determining theoverscheduling condition, to transmit a timing message to the networktermination system in a frequency band separate from a frequency bandassociated with the data stream to instruct the network terminationsystem to decrease a frequency of the clock signal in the remote timedomain.
 20. The apparatus of claim 14, wherein the scheduling processoris further configured to re-stamp an acknowledgement in the bandwidthallocation message in the local time domain based on the clock signal togenerate a re-stamped acknowledgement and to insert the re-stampedacknowledgement into the updated bandwidth allocation message, there-stamped acknowledgement corresponding to a time that a networktermination system received the upstream burst transmissions.